The present invention relates to a semiconductor device, particularly a chip-size package (CSP) type semiconductor device for treating signals of high frequency.
JP-A-4-19855, JP-A-6-237653, U.S. Pat. Nos. 5,679,977 and U.S. Pat. No. 5,801,441 disclose a wafer level chip-size package (CSP) type semiconductor device having a semiconductor element including a semiconductor electric circuit and electrically conductive terminal surface areas (first bonding pads) electrically connected to the semiconductor electric circuit, a first electrically insulating layer covering the semiconductor element while being prevented from covering at least a part of each of the first bonding pads, electrically conductive wires extending on the first electrically insulating layer, electrically connected at an end of each of the wires to the part of each of the first bonding pads so that the signals are input to the semiconductor electric circuit through the electrically conductive wires and/or output from the semiconductor electric circuit through the electrically conductive wires, and having an interface area (second bonding pad on which a bump electrode is formed) at another end of each of the wires, and a second electrically insulating layer covering the electrically conductive wires and the first electrically insulating layer while being prevented from covering at least a part of the another end of each of the wires.
An object of the present invention is to provide a chip-size package (CSP) type semiconductor device for treating signals of high frequency, in which device an excessive temperature increase is restrained and a thermal stress is decreased.
According to the present invention, a semiconductor device for treating signals of frequency not less than 800 MHz, comprises, a semiconductor element including a semiconductor electric circuit and an electrically conductive terminal surface area electrically connected to the semiconductor electric circuit, a first electrically insulating layer covering the semiconductor element while being prevented from covering at least a part of the electrically conductive terminal surface area, an electrically conductive wire extending on the first electrically insulating layer, electrically connected at an end of the wire to the part of the electrically conductive terminal surface area so that the signals are input to the semiconductor electric circuit through the electrically conductive wire and/or output from the semiconductor electric circuit through the electrically conductive wire, and having an interface area at another end of the wire, and a second electrically insulating layer covering the electrically conductive wire and the first electrically insulating layer while being prevented from covering at least a part of the interface area,
wherein a minimum thickness of the electrically conductive wire is determined along the following formula:       2    *                  2                  ω          ⁢                      xe2x80x83                    ⁢          μ          ⁢                      xe2x80x83                    ⁢          κ                       less than   h
when h is the minimum thickness of the electrically conductive wire, xcexa is an electrical conductivity of the electrically conductive wire, xcexc is a magnetic permeability of the electrically conductive wire, xcfx89 is an angular frequency of the signals transmitted through the electrically conductive wire.
Since the minimum thickness of the electrically conductive wire is determined along the following formula:       2    *                  2                  ω          ⁢                      xe2x80x83                    ⁢          μ          ⁢                      xe2x80x83                    ⁢          κ                       less than   h
the minimum thickness of the electrically conductive wire includes two times the skin depth caused by the skin effect established in the electrically conductive wire by the frequency of the signals and a central thickness other than the two times the skin depth so that a thermal energy or an electrically energy loss generated by an electric current through the skin depth is transmitted through the central thickness in which a flow of the electric current is restrained relatively in comparison with the skin depth. Therefore, an efficiency of thermal conductivity through the electrically conductive wire is kept high by the central thickness so that in the semiconductor device, an excessive temperature increase and/or a thermal stress is restrained.
If the entire length of the electrically conductive wire between the ends thereof is prevented from having thickness and/or width less than the minimum thickness, the efficiency of thermal conductivity through the electrically conductive wire is kept high over the entire length of the electrically conductive wire between the ends thereof so that the thermal conductivity is not throttled at any position over the entire length of the electrically conductive wire between the ends thereof.
It is preferable for keeping the total thickness of the electrically conductive wire small that the central thickness is not more than two times the skin depth or the skin depth. When the thermal conductivity needs to be kept high while keeping the total thickness of the electrically conductive wire small, the central thickness is not less than the skin depth and not more than two times the skin depth. For example, the central thickness is not more than 5 xcexcm, and/or the minimum thickness is not less than 4 xcexcm when the frequency of the signals is between 900 MHz and 1900 MHz.